A cork cell was first observed by Robert Hooke in the year: O 1556
O 1065
O 1965
O 1665

1665

Explanation:

In 1665, Robert Hooke was the first to observe cork cells and their characteristic hexagonal shape, using the first optical microscope, which was invented by him at that time.

out of these options:

ability to burn paper

pure sodium reacting violently with water

the boiling point of water

helium does not tend to react with anything

i would say this is a physical property:

helium does not tend to react with anything

why? :

i said helium does not tend to react with anything because well, it reacts to ! but ability to burn paper, pure sodium reacting violently with water, & the boiling point of water are chemical or

physical properties: the properties of a substance that can be observed without changing the chemical makeup of the substance

chemical properties: properties of a substance relating to the chemical nature and reactivity of the substance